ALDH2 and esophageal squamous cell carcinoma: In patients with esophageal SCC, multiple LVL (OR, 61.12; 95% CI, 5.4–691.64, p = 0.001), inactive ALDH2 (OR, 16.19; 95% CI, 1.15–228, p = 0.04) and current smoker (OR 8.02; 95% CI 1.09–59.22, p = 0.04) had significant risk factors for the development of synchronous and metachronous superficial head and neck SCC.22